A laser beam position sensing arrangement using two similar sensors where, instead of the first sensor being aligned normal to the beam scan path, the angle which bisects the two sensors is aligned normal to the beam scan path. The average of times T1 and T2 at which the laser beam is incident the respective sensors is used for the horizontal or start of scan value, and the difference (T2-T1) is proportional to the vertical or process direction value. From the difference between the two determined times, the longitudinal beam position may be determined.
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1. In an image forming apparatus utilizing a laser beam which executes a scan pattern of repeated transverse scans along a longitudinal line to form images on recording media, a process of determining the start of scan and the longitudinal beam position, comprising the steps of:
determining the time at which is laser beam reaches a first surface; determining the time at which the laser beam reaches a second surface which second surface extends obliquely to the first surface; averaging the two determined times to determine a start of scan reference time; forming the difference between the two determined times, deriving, from the difference between the two determined times, the longitdinal beam position; supplying a second laser beam; determining the time at which the second laser beam reaches a third surface; determining the time at which the second laser beam reaches a fourth surface, the fourth surface extending obliquely to the third surface; averaging the two determined times at which the second laser beam reaches a third surface and a fourth surface, respectively, to determine a start of scan reference time; forming the difference between the two determined times at which the second laser beam reaches a third surface and a fourth surface, respectively, deriving, from the difference between the two determined times at which the second laser beam reaches a third surface and a fourth surface, respectively, the longitudinal beam position of the second laser beam.
2. The process of
3. The process of
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1. Field of the invention
The present invention relates to image forming apparatus such as laser printers and more particularly to an arrangement for determining laser beam position.
2. Description of the Related Art
An in-line color laser image printing process where the media passes through four color developing stations in series will print the same speed as monochrome. The photo conductive drum exposures typically occur on all four colors at the same time. Both process and scan direction alignment of the four color developing stations is critical. The process location of each scanning laser beam must overlap to prevent color offset in the process direction. If one beam is out of synchronization with the others, the image in the corresponding color will be misaligned relative to the remaining color components, and the resulting image blurred. Each color should have an adjustment to correct for process direction misalignment because each color has a scanning laser beam following a separate optical path. Thermal changes will cause misalignment so the adjustment should be performed real time and not be just a one time manufacturing adjustment
It is possible to utilize a sensor arrangement for two dimensional beam detection known as PSD or Position Sensitive Detection. In such an arrangement, two optical sensors are used. One functions as a start of scan sensor to detect the horizontal scan beam location. A second sensor may be added at an angle to the first, and the time delay between the two sensors used to determine the vertical beam position location or so-called process direction. Firmware processes this information and makes appropriate adjustments in the raster image. Such an arrangement has a disadvantage in that the second sensor must be longer than the first to achieve the same vertical detection range. If the second sensor is offset by an angle of 45 degrees, the second sensor will be nearly 1.5 times longer than the first, which will be more expensive and may not be feasible.
It is highly desirable to implement an in-line process using four scanning lasers. What is needed in the art is a sensor arrangement which is capable of a full PSD function with reasonable expense.
The invention provides apparatus for determining the coordinates of the location of a laser beam utilizing first and second laser light sensitive sensors which are disposed obliquely to one another.
The invention comprises, in one form thereof, a color printer having multiple laser printheads, each employing a laser beam which executes a scan pattern of repeated transverse scans along a corresponding line to form image information, and laser beam position sensing arrays for each printhead synchronizing operation of the printheads. Each position sensing array includes first and second elongated laser light sensitive sensors extending obliquely to one another and to the corresponding laser scan line.
An advantage of the present invention is that sensor length and cost are reduced, and/or the effective range of process detection is increased.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
Referring now to the drawings and particularly to
In
The vertical sensitivity or change in signal vs. vertical position change depends on the angle (2A) between the sensors. Greater sensitivity can be achieved by increasing the angle, at the expense of lengthening both sensors or decreasing the vertical range. The angle is chosen to achieve a balance between sensor length which is directly related to cost, detection range, and sensitivity or accuracy.
The harmonization or corrective action may involve changing the laser timing or the timing of the photo conductive drum such as 22. For example, assume one laser longitudinal scan line is too low as indicated by scan line 34'. Assume further that the drum surface on which the laser beam impinges is moving vertically relative to the sensors of FIG. 2. Under these conditions, the speed of the corresponding photo conductive drum may be slowed slightly to relocate the scan line 34' at the correct location on the drum. With the same assumptions, commencing the laser beam scan earlier accomplishes the same correction.
While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. For example, this invention may be incorporated in image forming apparatus other than a laser printer, to include electrophotographic devices, copy machines, laser scanners, etc. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
Patent | Priority | Assignee | Title |
8139096, | Aug 14 2007 | S-PRINTING SOLUTION CO , LTD | Multi-color image forming apparatus and method of controlling the same |
8174552, | Aug 19 2009 | Eastman Kodak Company | Merging of image pixel arrangements |
8179412, | Aug 19 2009 | Eastman Kodak Company | Merging image pixels based on main-scan misalignment |
8373734, | Nov 12 2008 | HEWLETT-PACKARD DEVELOPMENT COMPANY, L P | Image forming apparatus and control method thereof |
9258454, | Feb 16 2006 | Hewlett-Packard Development Company, L.P. | Printer optical sensing error determination |
Patent | Priority | Assignee | Title |
4206348, | Jun 05 1978 | Eastman Kodak Company | Optical scanner with electrooptical feedback for beam positioning |
4270131, | Nov 23 1979 | Adaptive error correction device for a laser scanner | |
4569584, | Nov 24 1982 | Xerox Corporation | Color electrographic recording apparatus |
4686363, | Jan 21 1986 | Printware, Inc. | Self-resonant scanner biasing system |
4725855, | Apr 24 1985 | Hitachi Koki Co., Ltd.; Hitachi Ltd. | Multi-beam laser printer with beam spacing detection during blanking time |
4764672, | Dec 16 1986 | Structure of high-resolution polygon laser scanner | |
4823151, | Dec 26 1986 | Kabushiki Kaisha Toshiba | Multi-beam scanning system with sync signal generation based on single beam detection |
4845358, | May 28 1987 | Ricoh Co., Ltd. | Synchronizing device for laser printer |
4903067, | Apr 28 1987 | Canon Kabushiki Kaisha | Multiimage forming apparatus |
5032852, | Jan 27 1989 | Canon Kabushiki Kaisha | Image forming apparatus |
5072244, | Nov 30 1987 | Canon Kabushiki Kaisha | Superposed image forming apparatus with plural and adjustable image forming stations |
5115256, | Sep 14 1987 | Canon Kabushiki Kaisha | Beam recorder with scan position control |
5260725, | Sep 18 1992 | Xerox Corporation | Method and apparatus for registration of sequential images in a single pass, color xerographic printer |
5272493, | Apr 02 1992 | Xerox Corporation | Method and apparatus for registration of sequential images in a single pass, multi-LED printbar printer |
5291273, | Apr 19 1993 | Creo Products Inc. | Non-contact diameter measuring method and apparatus |
5302973, | Dec 16 1991 | Xerox Corporation | Method and apparatus for image registration in a single pass ROS system |
5319444, | Feb 16 1988 | Canon Kabushiki Kaisha | Position detecting method and apparatus |
5319537, | Dec 10 1992 | Xerox Corporation | Raser output scanner color printer with improved start of scan detection and process registration |
5351264, | Feb 14 1992 | Canon Kabushiki Kaisha | Optical apparatus for emitting light and automatic adjustment apparatus therefor |
5381167, | Oct 24 1991 | Konica Corporation | Color image forming apparatus |
5384592, | Nov 16 1992 | Xerox Corporation | Method and apparatus for tandem color registration control |
5452073, | Jan 14 1992 | Canon Kabushiki Kaisha | Multi-image forming apparatus having registration error correction |
5457487, | Jan 08 1992 | Canon Kabushiki Kaisha | Color image forming apparatus which times release of each of plural color image signals |
5465154, | May 05 1989 | Optical monitoring of growth and etch rate of materials | |
5477330, | Oct 16 1992 | Printware, Inc. | Synchronization to a start-of-scan detection, and digital generation of variable frequencies, from a fixed-frequency fixed-phase frequency source in an image generator in order to highly accurately time the placement of pixels upon a scan line |
5525809, | Oct 26 1994 | Minnesota Mining and Manufacturing Company | Electro-optic sheet-sensing apparatus and method having a movable light emitting element |
5530242, | Feb 13 1995 | Xerox Corporation | Fiber optic scanning beam detector with Start-Of-Scan detection |
5539719, | Feb 17 1994 | Konica Corporation | Light beam deviation detecting device used in an image forming apparatus |
5583557, | Jun 29 1993 | Konica Corporation | Image forming apparatus which corrects a deviation in a distance between plural light beams |
5677726, | May 26 1994 | Konica Corporation | Image reading apparatus |
5694637, | Sep 14 1995 | Konica Corporation | Method for controlling an image forming apparatus which uses plural laser beams |
5737003, | Nov 17 1995 | Imation Corp. | System for registration of color separation images on a photoconductor belt |
5745154, | Jan 13 1995 | Fuji Xerox Co., Ltd. | Digital image forming apparatus with scan synchronization |
5754690, | Oct 27 1995 | Xerox Corporation | Position sensitive detector based image conversion system capable of preserving subpixel information |
5790255, | Feb 10 1997 | Xerox Corporation | Transparent light beam detectors |
5844591, | Sep 08 1994 | FUJI XEROX CO , LTD | Multibeam laser recording apparatus |
5864127, | Oct 10 1996 | Xerox Corporation | Analog glyph detector and detector arrays |
5864404, | Dec 31 1996 | I E S S P A ; DATASENSOR S P A ; DATALOGIC S P A | Process and apparatus for measuring the volume of an object by means of a laser scanner and a CCD detector |
5982402, | Sep 08 1994 | Fujitsu Limited | Apparatus for printing color image by combination of optical beam scanning units and photosensitive drums |
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